In Valdeluz, a town outside Madrid that was envisioned as a commuter's paradise when it was created 15 years ago, there was always supposed to be a school. And a private one, for kindergartners to high schoolers, opened in September 2007 — just a year before the global financial crisis burst Spain's property bubble.

Soon enough, Valdeluz turned into one of Spain's infamous "cuidades fantasma," or ghost towns, filled with unwanted property and unfinished construction. Homeowners defaulted on mortgages, real estate promoters went bankrupt, and houses were repossessed. The school, half-built and meant to accommodate 1,500 students, shut down in